1. Field
The invention is in the field of high brightness laser systems which was a low energy master oscillator laser beam and a power amplifier usually limited to a low pulse repetition rate, and specifically to the time multiplexing of a plurality of phase conjugated power amplifiers in which succeeding oscillator laser beam pulses are reflected off rotating mirrors and directed toward each of a plurality of phase conjugated power amplifiers in a Gatling gun fashion of firing the amplifiers either sequentially or in bursts to provide a high pulse repetition rate for the laser system.
2. Prior Art
High brightness lasers are often of the design which involves a master oscillator and a power amplifier. When using solid state lasers, the maximum pulse repetition frequency (PRF) of these lasers is usually limited by thermal effects in the power amplifier laser rods. The PRF of the power amplifiers is usually limited to about 60 Hertz. Sufficiently low power master oscillators may be operated at arbitrarily high PRFs. One known high brightness laser which is limited in frequency is a laser oscillator and in optical alignment therewith a polarizer which pases the oscillator laser beam therethrough directly into a phase conjugate power amplifier. The solid state laser rod type amplifier has a quarter-wave plate at its output and a phase conjugate mirror comprised of a focusing lens and a stimulated Brillouin scattering cell. The quarter-wave plate converts the incident linearly polarized beam from the oscillator laser to circular polarization, the lens focuses the beam into the cell, and the cell retroreflects the beam back out and through the quarter-wave plate which converts the beam back to a linear polarization that is rotated by 90.degree. from the original polarization. The 90.degree. polarization rotated beam is amplified by the amplifier on the second pass therethrough and is reflected off the polarizer as an output beam from the laser system.
It has previously been demonstrated that stimulated Brillouin scattering of a laser beam results in a phase conjugated and distortion-free retroreturn of the incident laser beam even in the presence of a phase aberrator. Furthermore, the directionality of the output is not affected by any vibrations or small movements of the amplifier. Such a phase conjugate amplifier laser system is characterized by high-fidelity amplification and a stable output beam direction. The heat generated in the laser rods however limit their frequency of laser pulse amplification.
The present invention provides an increased pulse repetition frequency by the use of a plurality of the solid state laser rod type amplifiers and synchronously time-multiplexing the oscillator laser beam pulses sequentially into each of the plurality of amplifiers so that each individual amplifier operates at a rate of say no higher than 60 Hertz so that the individual amplifiers will not overheat. The outputs from each amplifier is automatically and stably aligned with the outputs of the other amplifiers. The result is an amplified laser output beam from the system which has a pulse repetition frequency of a single amplifier times the number of amplifiers.
A similar patent application is concurrently filed, titled "Gatling Gun Laser Amplifier Using An Optical Diode" by the present co-inventors and Richard Utano. The other application is however distinctly different from the present invention.